The invention relates to overbed tables. Such tables are used in hospitals, nursing homes and the like where there is a need for a table which may be raised and lowered for a use by a person in a bed or a chair.
Overbed tables typically have a wheeled base supporting a vertical pedestal column which telescopically receives another vertical pedestal column which supports a table. The base is typically wheeled under the bed, with the table extending over the patient lying or sitting on the bed. The pedestal columns are vertically moveable relative to each other and have a latching mechanism for locking the columns and hence the table in a given desired vertical position.
One type of latch mechanism for an overbed table is the ratchet and pawl type wherein a vertical element has a series of holes or dents into which a pin or pawl is inserted. One of the objections to this mechanism is that it does not afford infinite type adjustment. Another objection is that it can come to rest with the pawl out of engagement with the ratchet, so that the table falls to the first available hole when load is applied.
Another latching mechanism is the clutch spring type. This mechanism provides infinite adjustment, however the conversion of rotary action of the clutch mechanism to the vertical linear action of the table usually results in an expensive overall design.
Another mechanism for latching and supporting overbed tables is the cam plate type. This mechanism is similar to the ratchet and pawl type, but a plate is pivotally mounted to the vertically moving column in a near horizontal plane and is forced into contact with the inner surface of the fixed column by a spring. As load is applied, the plate rotates to a more nearly horiztonal position digging one edge into the fixed column. After repeated uses of the latch, the inner surface of the outer column has numerous dents caused by the latch plate. Operation of the table becomes noisy, and operation of the release mechanism requires considerable force. This mechanism is also very sensitive to tolerances of the parts during construction.
The present invention provides a support assembly for an overbed table employing a wedge and roller clutch mechanism for latching the table, including particularly desirable wedge and roller clutch structure and features. The present support assembly is simple in design, and affords efficiency in manufacturing assembly. A valuable aspect of the design is its adaptability to a wide range of part tolerances, thus affording economical manufacture.
The invention is further characterized by its highly desirable operating characteristics, including counterbalancing of the table, aiding lifting thereof, and silent vertical positioning of the table, which is particularly desirable in hospitals and nursing homes.